WASHINGTON -- The Senate voted 51-48 yesterday to keep the limping B-2 stealth bomber program alive for another year, despite a recent test suggesting that the plane may not be so stealthy after all.

Vice President Dan Quayle, who presided in case his tie-breaking vote was needed, announced the tally to a crowded chamber after a day of debate over the fate of the controversial warplane. Since the House already had voted to end the program, a Senate vote to do the same would have killed it.

The three-vote margin was a sharp drop from the most recent Senate vote Aug. 1, when the B-2 prevailed 57-42. But since then, the Soviet Union has dissolved and the B-2 has failed a key test of its radar-evading capability, the major justification for its record $865 million-per-plane price tag.

The vote, amid Senate action on the Pentagon's $269.7 billion 1992 spending bill, may be only a temporary reprieve. Even B-2 boosters agree that the Air Force is not likely to get the full 75-plane fleet it wants.

The Senate vote to appropriate $3.2 billion to buy four planes in 1992 and $1.6 billion for development still has to clear a conference committee. President Bush has threatened to veto any defense bill that does not include money for more B-2s.

"I think the failed test precipitated a lot of thinking around here," said Sen. Dale Bumpers, D-Ark., who complained that the Air Force has repeatedly sought new missions for the bomber as the Soviet threat has dwindled.

The Air Force already has bought 15 B-2s for $30 billion and wants to spend $34.8 billion for 60 more.

The first three planes are flying, but the Pentagon was shaken when one of them failed a July 26 test of its ability to elude enemy radar.